In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving spectral efficiency and improving data rates, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing high-speed data rates, providing low delay and so on, long-term evolution (LTE) has been under study (see, for example, non-patent literature 1).
In the third-generation mobile communication system, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. Meanwhile, in a system of the LTE scheme (LTE system), it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band which ranges from 1.4 MHz to 20 MHz. Furthermore, in the UMTS network, for the purpose of achieving further broadbandization and higher speed, successor systems of LTE have been under study (for example, LTE-Advanced (LTE-A)). For example, in LTE-A, there is a plan to expand the maximum systems band for LTE specifications, which is 20 MHz, to approximately 100 MHz on the downlink and to approximately 40 to 60 MHz on the uplink.
Now, in the LTE system, measuring uplink channel quality in a radio base station apparatus (BS: Base Station) based on an SRS (Sounding Reference Signal) that is provided for channel quality measurement and that is transmitted from a mobile terminal apparatus (UE: User Equipment) is under study (see, for example, non-patent literature 2). In this case, the radio base station apparatus performs scheduling to allow the mobile terminal apparatus to transmit an uplink shared channel (PUSCH: Physical Uplink Shared CHannel) signal based on the channel quality measurement result, and issues a command using a downlink control channel. (PDCCH: Physical Downlink Control CHannel). In release-8 LTE, the SRS is multiplexed on the last symbols of subframes constituting an uplink radio frame, and is transmitted periodically from the mobile terminal apparatus to the radio base station apparatus.